Morphology of Flowering Plants
Tap Root System: In majority of the dicotyledonous plants, the direct
elongation of the radicle leads to the formation of primary root which grows
inside the soil. It bears lateral roots of several orders that are referred to
as secondary, tertiary, etc. roots. The primary roots and its branches
constitute the tap root system, as seen in the mustard plant.
Fibrous Root System: In monocotyledonous plants, the primary root is
short lived and is replaced by a large number of roots. These roots originate
from the base of the stem and constitute the fibrous root system, as seen in the
Adventitious Roots: In some plants, like grass, Monstera and the banyan
tree, roots arise from parts of the plant other than the radicle and are called
Functions of Roots: The main functions of the root system are absorption
of water and minerals from the soil, providing a proper anchorage to the plant
parts, storing reserve food material and synthesis of plant growth regulators.
Regions of the Root
The root is covered at the apex by a thimble-like structure called the root cap.
It protects the tender apex of the root as it makes its way through the soil. A
few millimetres above the root cap is the region of meristematic activity. The
cells of this region are very small, thin-walled and with dense protoplasm. They
divide repeatedly. The cells proximal to this region undergo rapid elongation
and enlargement and are responsible for the growth of the root in length. This
region is called the region of elongation. The cells of the elongation zone
gradually differentiate and mature. Hence, this zone, proximal to region of
elongation, is called the region of maturation. From this region some of the
epidermal cells form very fine and delicate, thread-like structures called root
hairs. These root hairs absorb water and minerals from the soil.
Modifications of Root
Roots in some plants change their shape and structure and become modified to
perform functions other than absorption and conduction of water and minerals.
They are modified for support storage of food and respiration.
Modification for Food Storage: Tap roots of carrot, turnips and
adventitious roots of sweet potato, get swollen and store food.
Modification for Support: Banyan trees, after growing to a large size,
develop hanging roots from branches. These are called prop roots. Similarly, the
stems of maize and sugarcane have supporting roots coming out of the lower nodes
of the stem. These are called stilt roots.
Modification for Respiration: In some plants such as Rhizophora growing
in swampy areas, many roots come out of the ground and grow vertically upwards.
Such roots, called pneumatophores, help to get oxygen for respiration.
The stem is the ascending part of the axis bearing branches, leaves, flowers and
fruits. It develops from the plumule of the embryo of a germinating seed. The
stem bears nodes and internodes. The region of the stem where leaves are born
are called nodes while internodes are the portions between two nodes. The stem
bears buds, which may be terminal or axillary. Stem is generally green when
young and later often become woody and dark brown.
Functions of Stem: The main function of the stem is spreading out branches
bearing leaves, flowers and fruits. It conducts water, minerals and
photosynthates. Some stems perform the function of storage of food, support,
protection and of vegetative propagation.
Modifications of Stem
Stems are modified to perform different functions. Underground stems of potato,
ginger, turmeric, zaminkand, Colocasia are modified to store food in them. They
also act as organs of perenation to tide over conditions unfavourable for
growth. Stem tendrils which develop from axillary buds, are slender and spirally
coiled and help plants to climb such as in gourds (cucumber, pumpkins,
watermelon) and grapevines. Axillary buds of stems may also get modified into
woody, straight and pointed thorns. Thorns are found in many plants such as
Citrus, Bougainvillea. They protect plants from browsing animals. Some plants of
arid regions modify their stems into flattened (Opuntia), or fleshy cylindrical
(Euphorbia) structures. They contain chlorophyll and carry out photosynthesis.
Underground stems of some plants such as grass and strawberry, etc., spread to
new niches and when older parts die new plants are formed. In plants like mint
and jasmine a slender lateral branch arises from the base of the main axis and
after growing aerially for some time arch downwards to touch the ground. A
lateral branch with short internodes and each node bearing a rosette of leaves
and a tuft of roots is found in aquatic plants like Pistia and Eichhornia. In
banana, pineapple and Chrysanthemum, the lateral branches originate from the
basal and underground portion of the main stem, grow horizontally beneath the
soil and then come out obliquely upward giving rise to leafy shoots.
The leaf is a lateral, generally flattened structure borne on the stem. It
develops at the node and bears a bud in its axil. The axillary bud later
develops into a branch. Leaves originate from shoot apical meristems and are
arranged in an acropetal order. They are the most important vegetative organs
A typical leaf consists of three main parts: leaf base, petiole and lamina. The
leaf is attached to the stem by the leaf base and may bear two lateral small
leaf like structures called stipules. In monocotyledons, the leaf base expands
into a sheath covering the stem partially or wholly.
In some leguminous plants the leafbase may become swollen, which is called the
pulvinus. The petiole help hold the blade to light. Long thin flexible petioles
allow leaf blades to flutter in wind, thereby cooling the leaf and bringing
fresh air to leaf surface.
The lamina or the leaf blade is the green expanded part of the leaf with veins
and veinlets. There is, usually, a middle prominent vein, which is known as the
midrib. Veins provide rigidity to the leaf blade and act as channels of
transport for water, minerals and food materials. The shape, margin, apex,
surface and extent of incision of lamina varies in different leaves.
The arrangement of veins and the veinlets in the lamina of leaf is termed as
venation. When the veinlets form a network, the venation is termed as
reticulate. When the veins run parallel to each other within a lamina, the
venation is termed as parallel. Leaves of dicotyledonous plants generally
possess reticulate venation, while parallel venation is the characteristic of
Types of Leaves
A leaf is said to be simple, when its lamina is entire or when incised, the
incisions do not touch the midrib. When the incisions of the lamina reach up to
the midrib breaking it into a number of leaflets, the leaf is called compound. A
bud is present in the axil of petiole in both simple and compound leaves, but
not in the axil of leaflets of the compound leaf.
The compound leaves may be of two types. In a pinnately compound leaf a number
of leaflets are present on a common axis, the rachis, which represents the
midrib of the leaf as in neem. In palmately compound leaves, the leaflets are
attached at a common point, i.e., at the tip of petiole, as in silk cotton.
Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. This
is usually of three types – alternate, opposite and whorled.
Alternate Arrangement of Leaves: In alternate type of phyllotaxy, a
single leaf arises at each node in alternate manner, as in china rose, mustard
and sun flower plants.
Opposite Arrangement of Leaves: In opposite type, a pair of leaves arise
at each node and lie opposite to each other as in Calotropis and guava plants.
Whorled Arrangement of Leaves: If more than two leaves arise at a node
and form a whorl, it is called whorled, as in Alstonia.
Modifications of Leaves
Leaves are often modified to perform functions other than photosynthesis.
Tendrils: They are converted into tendrils for climbing as in peas or
into spines for defence as in cacti.
Bulb: The fleshy leaves of onion and garlic store food.
In some plants such as Australian acacia, the leaves are small and short-lived.
The petioles in these plants expand, become green and synthesise food. Leaves of
certain insectivorous plants such as pitcher plant, venus-fly trap are also
A flower is a modified shoot wherein the shoot apical meristem changes to floral
meristem. Internodes do not elongate and the axis gets condensed. The apex
produces different kinds of floral appendages laterally at successive nodes
instead of leaves. When a shoot tip transforms into a flower, it is always
solitary. The arrangement of flowers on the floral axis is termed as
inflorescence. Depending on whether the apex gets converted into a flower or
continues to grow, two major types of inflorescences are defined – racemose and
Racemose Inflorescence: In racemose type of inflorescences the main axis
continues to grow, the flowers are borne laterally in an acropetal succession.
Acropetal succession means that older flowers are at the base and younger
flowers are near the apex.
Cymose Inflorescence: In cymose type of inflorescence the main axis
terminates in a flower, hence is limited in growth. The flowers are borne in a
basipetal order. In basipetal succession older flowers are at the apex and
younger flowers are near the base.
The flower is the reproductive unit in the angiosperms. It is meant for sexual
reproduction. A typical flower has four different kinds of whorls arranged
successively on the swollen end of the stalk or pedicel, called thalamus or
receptacle. These are calyx, corolla, androecium and gynoecium. Calyx and
corolla are accessory organs, while androecium and gynoecium are reproductive
organs. In some flowers like lily, the calyx and corolla are not distinct and
are termed as perianth.
When a flower has both androecium and gynoecium, it is bisexual. A flower having
either only stamens or only carpels is unisexual.
Symmetry of Flowers: In symmetry, the flower may be actinomorphic (radial
symmetry) or zygomorphic (bilateral symmetry). When a flower can be divided into
two equal radial halves in any radial plane passing through the centre, it is
said to be actinomorphic, e.g., mustard, datura, chilli. When it can be divided
into two similar halves only in one particular vertical plane, it is
zygomorphic, e.g., pea, gulmohur, bean, Cassia. A flower is asymmetric
(irregular) if it cannot be divided into two similar halves by any vertical
plane passing through the centre, as in canna.
A flower may be trimerous, tetramerous or pentamerous when the floral appendages
are in multiple of 3, 4 or 5, respectively. Flowers with bracts, reduced leaf
found at the base of the pedicel, are called bracteate and those without bracts,
Hypogynous Flower: Based on the position of calyx, corolla and androecium
in respect of the ovary on thalamus, the flowers are described as hypogynous
perigynous and epigynous. In the hypogynous flower the gynoecium occupies the
highest position while the other parts are situated below it. The ovary in such
flowers is said to be superior, e.g., mustard, china rose and brinjal.
Perigynous Flower: If gynoecium is situated in the centre and other parts
of the flower are located on the rim of the thalamus almost at the same level,
it is called perigynous. The ovary here is said to be half inferior, e.g., plum,
Epigynous Flower: In epigynous flowers, the margin of thalamus grows
upward enclosing the ovary completely and getting fused with it, the other parts
of flower arise above the ovary. Hence, the ovary is said to be inferior as in
flowers of guava and cucumber, and the ray florets of sunflower.
Parts of a Flower: Each flower normally has four floral whorls, viz.,
calyx, corolla, androecium and gynoecium.
Calyx: The calyx is the outermost whorl of the flower and the members are
called sepals. Generally, sepals are green, leaf like and protect the flower in
the bud stage. The calyx may be gamosepalous (sepals united) or polysepalous
Corolla: Corolla is composed of petals. Petals are usually brightly
coloured to attract insects for pollination. Like calyx, corolla may be also
free (gamopetalous) or united (polypetalous). The shape and colour of corolla
vary greatly in plants. Corolla may be tubular, bell-shaped, funnel-shaped or
Aestivation: The mode of arrangement of sepals or petals in floral bud
with respect to the other members of the same whorl is known as aestivation. The
main types of aestivation are valvate, twisted, imbricate and vexillary.
Valvate: When sepals or petals in a whorl just touch one another at the
margin, without overlapping, as in Calotropis, it is said to be valvate.
Twisted: If one margin of the appendage overlaps that of the next one and
so on as in china rose, lady’s finger and cotton, it is called twisted.
Imbricate: If the margins of sepals or petals overlap one another but not
in any particular direction as in Cassia and gulmohur, the aestivation is called
Vexillary: In pea and bean flowers, there are five petals, the largest
(standard) overlaps the two lateral petals (wings) which in turn overlap the two
smallest anterior petals (keel); this type of aestivation is known as vexillary
Androecium is composed of stamens. Each stamen which represents the male
reproductive organ consists of a stalk or a filament and an anther. Each anther
is usually bilobed and each lobe has two chambers, the pollen-sacs. The pollen
grains are produced in pollen-sacs. A sterile stamen is called staminode.
Stamens of flower may be united with other members such as petals or among
themselves. When stamens are attached to the petals, they are epipetalous as in
brinjal, or epiphyllous when attached to the perianth as in the flowers of lily.
The stamens in a flower may either remain free (polyandrous) or may be united in
varying degrees. The stamens may be united into one bunch or one bundle
(monoadelphous) as in china rose, or two bundles (diadelphous) as in pea, or
into more than two bundles (polyadelphous) as in citrus. There may be a
variation in the length of filaments within a flower, as in Salvia and mustard.
Gynoecium is the female reproductive part of the flower and is made up of one or
more carpels. A carpel consists of three parts namely stigma, style and ovary.
Ovary is the enlarged basal part, on which lies the elongated tube, the style.
The style connects the ovary to the stigma. The stigma is usually at the tip of
the style and is the receptive surface for pollen grains. Each ovary bears one
or more ovules attached to a flattened, cushion-like placenta. When more than
one carpel is present, they may be free (as in lotus and rose) and are called
apocarpous. They are termed syncarpous when carpels are fused, as in mustard and
tomato. After fertilisation, the ovules develop into seeds and the ovary matures
into a fruit.
Placentation: The arrangement of ovules within the ovary is known as
placentation. The placentation are of different types namely, marginal, axile,
parietal, basal, central and free central.
Marginal: In marginal placentation the placenta forms a ridge along the
ventral suture of the ovary and the ovules are borne on this ridge forming two
rows, as in pea.
Axile: When the placenta is axial and the ovules are attached to it in a
multilocular ovary, the placentaion is said to be axile, as in china rose,
tomato and lemon.
Parietal: In parietal placentation, the ovules develop on the inner wall
of the ovary or on peripheral part. Ovary is one-chambered but it becomes
two-chambered due to the formation of the false septum, e.g., mustard and
Argemone. When the ovules are borne on central axis and septa are absent, as in
Dianthus and Primrose the placentation is called free central.
Basal: In basal placentation, the placenta develops at the base of ovary
and a single ovule is attached to it, as in sunflower, marigold.
The fruit is a characteristic feature of the flowering plants. It is a mature or
ripened ovary, developed after fertilisation. If a fruit is formed without
fertilisation of the ovary, it is called a parthenocarpic fruit. Generally, the
fruit consists of a wall or pericarp and seeds. The pericarp may be dry or
fleshy. When pericarp is thick and fleshy, it is differentiated into the outer
epicarp, the middle mesocarp and the inner endocarp.
In mango and coconut, the fruit is known as a drupe. They develop from
monocarpellary superior ovaries and are one seeded. In mango the pericarp is
well differentiated into an outer thin epicarp, a middle fleshy edible mesocarp
and an inner stony hard endocarp. In coconut which is also a drupe, the mesocarp
The ovules after fertilisation, develop into seeds. A seed is made up of a seed
coat and an embryo. The embryo is made up of a radicle, an embryonal axis and
one (as in wheat, maize) or two cotyledons (as in gram and pea).
Structure of a Dicotyledonous Seed
The outermost covering of a seed is the seed coat. The seed coat has two layers,
the outer testa and the inner tegmen. The hilum is a scar on the seed coat
through which the developing seeds were attached to the fruit. Above the hilum
is a small pore called the micropyle. Within the seed coat is the embryo,
consisting of an embryonal axis and two cotyledons. The cotyledons are often
fleshy and full of reserve food materials. At the two ends of the embryonal axis
are present the radicle and the plumule. In some seeds such as castor the
endosperm formed as a result of double fertilisation, is a food storing tissue.
In plants such as bean, gram and pea, the endosperm is not present in mature
seeds and such seeds are called nonendospermous.
Structure of Monocotyledonous Seed
Generally, monocotyledonous seeds are endospermic but some as in orchids are
non-endospermic. In the seeds of cereals such as maize the seed coat is
membranous and generally fused with the fruit wall. The endosperm is bulky and
stores food. The outer covering of endosperm separates the embryo by a
proteinous layer called aleurone layer. The embryo is small and situated in a
groove at one end of the endosperm. It consists of one large and shield shaped
cotyledon known as scutellum and a short axis with a plumule and a radicle. The
plumule and radicle are enclosed in sheaths which are called coleoptile and
SEMI-TECHNICAL DESCRIPTION OF A TYPICAL FLOWERING PLANT
description has to be brief, in a simple and scientific language and presented
in a proper sequence. The plant is described beginning with its habit,
vegetative characters – roots, stem and leaves and then floral characters
inflorescence and flower parts.
Fusion is indicated by enclosing the figure within bracket and adhesion by a
line drawn above the symbols of the floral parts. A floral diagram provides
information about the number of parts of a flower, their arrangement and the
relation they have with one another. The position of the mother axis with
respect to the flower is represented by a dot on the top of the floral diagram.
Calyx, corolla, androecium and gynoecium are drawn in successive whorls, calyx
being the outermost and the gynoecium being in the centre.
DESCRIPTION OF SOME IMPORTANT FAMILIES
This family was earlier called Papilonoideae, a subfamily of family Leguminosae.
It is distributed all over the world.
Vegetative Characters: Trees, shrubs, herbs; root with root nodules
Stem: erect or climber
Leaves: alternate, pinnately compound or simple; leaf base, pulvinate;
stipulate; venation reticulate.
Flower: bisexual, zygomorphic
Calyx: sepals five, gamosepalous; imbricate aestivation
Corolla: petals five, polypetalous, papilionaceous, consisting of a
posterior standard, two lateral wings, two anterior ones forming a keel
(enclosing stamens and pistil), vexillary aestivation
Androecium: ten, diadelphous, anther dithecous
Gynoecium: ovary superior, mono carpellary, unilocular with many ovules,
Fruit: legume; seed: one to many, non-endospermic
Economic importance: Many plants belonging to the family are sources of
pulses (gram, arhar, sem, moong, soyabean; edible oil (soyabean, groundnut); dye
(indigofera); fibres (sunhemp); fodder (Sesbania, Trifolium), ornamentals
(lupin, sweet pea); medicine (muliathi).
It is a large family, commonly called as the ‘potato family’. It is widely
distributed in tropics, subtropics and even temperate zones.
Vegetative Characters: Plants mostly, herbs, shrubs and small trees
Stem: herbaceous rarely woody, aerial; erect, cylindrical, branched,
solid or hollow, hairy or glabrous, underground stem in potato (Solanum
Leaves: alternate, simple, rarely pinnately compound, exstipulate;
Inflorescence : Solitary, axillary or cymose as in Solanum
Flower: bisexual, actinomorphic
Calyx: sepals five, united, persistent, valvate aestivation
Corolla: petals five, united; valvate aestivation
Androecium: stamens five, epipetalous
Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular, placenta
swollen with many ovules
Fruits: berry or capsule
Seeds: many, endospermous
Economic Importance: Many plants belonging to this family are source of
food (tomato, brinjal, potato), spice (chilli); medicine (belladonna,
ashwagandha); fumigatory (tobacco); ornamentals (petunia).
Commonly called the ‘Lily family’ is a characteristic representative of
monocotyledonous plants. It is distributed world wide.
Vegetative characters: Perennial herbs with underground bulbs/corms/
Leaves: mostly basal, alternate, linear, exstipulate with parallel
Inflorescence: solitary / cymose; often umbellate clusters
Flower: bisexual; actinomorphic
Perianth: petal six (3+3), often united into tube; valvate aestivation
Androcium: stamen six, (3+3)
Gynoecium: tricarpellary, syncarpous, ovary superior, trilocular with
many ovules; axile placentation
Fruit: capsule, rarely berry
Economic Importance: Many plants belonging to this family are good
ornamentals (tulip, Gloriosa), source of medicine (Aloe), vegetables
(Asparagus), and colchicine (Colchicum autumnale).